Glow-discharge transmitter



,P. THOMAS eLow DISCHARGE TRANSMITTER ay 3, 19527. I wmfi Filed Nov. 14. 1922 WITNESSES: INVENTOR r v I S I V I'D/#7605 mamas f v BY f ATTORNEY Patented May 3,1921;

UNITED STATES PHILLIPS THOMAS, OF EDGEWOOD PARK,

HOUSE ELECTRIC VANIA.

1,626,646 PATENT OFFICE.

PENNSYLVANIA, Assrenoa To wEsTING- & MANUFACTURING eoMPAnY, A CORPORATION or PENNSYL- GLOW-DISCHARGE TRANSMITTER.

Application filed November 14, 1922. Serial No, 600,828.

My invention relatesto telephone systems I and apparatus and particularly-to improved sound-wave translating devices.

In its broadest aspect, an object of my invention is to provide a translating device which is capable of effecting an interchange of energy betweena fluid medium subject tovibratory motion and an electrical circuit subject to pulsating electrical currents.

More specifically an object of my invention is to provide a translating device of the class described, wherein sound waves are faithfully translated into correspondingly modulated electrical energy without impairingthe uality, tone and quantity of the translated energy.

Another object of my invention is to provide a telephone translating apparatus which embodies no moving parts and more especially one wherein the usual vibratory diaphragm may be eliminated.

A further object of my invention to provide a sound wave translatin device which is characterized by its simp icity of design and operation and which lends itself to nexpensive methods of manufacture, wherein the'several parts may be easily made by existing. automatic machiner and may be readily assembled with a minimum ex penditure of time and of money.

In practicing my invention, I provide a translating device comprising a pair of spaced electrodes andan energizin circuit therefor designed to establish a g ow 'discharge between the pair of electrodes. I

have found that the voltage-current charac-.

teristic of the glow discharge varies. in accordance with variat ons 1n the ressure of the medium surrounding the disc arge.

4 Ina preferred form of embodiment of my invention, the current through the dis:

In a modified form of my invention, the voltage across the discharge electrodes rather than the currents traversing the path therebetween is maintained substantially c'on stant to allow pressure variations to effectcorresponding variations in the intensity of the currents lnthe discharge. The as means of a repeater rent variations may be translated by means of a transformer, into potential variations and impressed upon the input terminals of a repeater device, as in the preferred embodiment just ment1one'd:

y In the development of my invention, considerable difficulty was experienced in establishing and maintaining a low discharge between the discharge electro es. Furthermore, the discharge, when once established, was likely to be very noisy in operation. After considerable experimental work, involving tests of man well known materials as discharge electro es, I have foundthat discharge electrodes of copper permit the easy establishment and maintenance of a glow discharge which is very quiet in operation. The discharge between the electrodes may be made more steady by employing pointedelectrodes, since the discharge normally tends to operate between points.

Further difiiculty was encountered in the tendency for the discharge to assume, at

times, an insensitive condition, wherein the voltage-current characteristic is only slightly affected by'variations in pressure. As the electrodes age in service, a condition arises where the low sensitive state becomes permanent. This 'difliculty was overcome by causing the dischargeto operate in a mag netic field which is parallel to the path of the discharge.

I A still further difficulty was encountered -1n the employment of shielding means for the supply conductors leading to .the discharge electrodes, inasmuch as theglow discharge tends to become unsteady by the use of the same. This difficulty is overcome by inserting a relativel high impedance in'one,

or more of said 'disc arge supply conductors immediately. adjacent to the corresponding discharge electrodes. 7

With these and other objects and applications in view,'my invention further consists in the nature, the mode of operation and the constructional details hereinafter described and claimed and illustrated in the accompanying drawing, wherein:

Figure 1 is a view, partially diagrammatic and partially structural, ofcircuits and apparatus embodying a preferred form of my invention; I

Figure 2 is. an enlarged detail view showmg the discharge electrodes of- Fig. 1 and v illustrating the several component parts of a glow discharge;

Fig. 3 is a view similar to Fig. 1 but showing a modification.

In the form of embodiment of my invention shown in Fig. 1, a pair of pointed discharge electrodes, 1 and 2 consisting, preferably of copper material, are secured, respectively, to adjacent ends of a pair of magnetizable members 3 and 4. The magnetizable members 3 and 4 are, in turn, connected by conductors 5 and 6, respectively, to the plus and minus terminals of a source of direct-current energy (not shown). As previously statedjit was found that a glow discharge could be easily established and maintained between electrodes of copper, which was practically impossible for the other materials, as manganese, iron and nickel. Subsequent experimental work with tungsten, silver and platinum brought out the fact that a glow discharge could be establishedand maintained between electrodes of such materials. but that such discharge was very noisy, in comparison with the one established between copper electrodes.

A resistor 7 may be connected in seriescircuit relation with the conductor 6 and serves to maintain the current therethrough substantially constant, not withstanding slight variations in the impedance of the glow-discharge path. In practice, it

was found that the electromotive force of 'the energy source (not shown) may be on the order of 6000 volts and that the resistance of the resistor 7 may be on" the order'of a megohm.

When the discharge electrodes 1 and 2 are separated a certain amount, say of I an inch for a system having the constants just indicated, a glow discharge is established therebetween which difiers in several important respects from the ordinary type of arc discharge. That is to say, in the glow discharge, the electrodes 1 and 2 remain relatively cool during operation; there is substantially no vaporization or melting or burning or disintegrating of the electrodes; the hot spot peculiar to the ordiprises the following nary arc is entirely absent; and the discharge takesplace in a steady, quiet and smooth manner. The latter characteristic is of especial importance since the variations .in the voltage-current characteristic of the discharge for fluctuations of the same may be comparable to thevcharacteristic variations caused by sound waves, as will be apparent more fully hereinafter.

The glow discharge just mentioned comortions arranged in their respective order etween the negative electrode 2 and the ositive electrode 1;

namely, a negative lig t 8, which is in immediate contact with the negative electrode 2; a cathode dark space 9, sometimes known f as, Crookesdark space; a cathode glOW 11;

a Faraday dark space 12"; anda positive or anode column 13, which terminates on the to maintain the currents therethrough substantially independent of slight potential variations, in the glow discharge, the effect, of pressure variations, as produced by sound waves, is to cause corresponding potential variations across the discharge electrodes 1 and 2 having a wave form corresponding to that of the pressure variations.

The potential drop across the discharge electrodes 1 and 2 is thus composed of a constant component, namely the so-called quiet voltage drop and an alternating, component which. corresponds to the sound waves. ,1 w

The alternating component of voltage just mentioned may be translated into amplified currents of similar wave form by impressing the same through conductors 14 and 15 upon the grid and filament elements 16 and 17, respectively, of a three-electrode vacuum tube 18, including in addition a plate element 19.

A condenser 21. having a negligible impedance to currents of sound-wave frequency, is included in the grid conductor 14 and serves to prevent the so-called quiet voltage drop across the discharge electrodes 1 and 2 from operating to effect the blocking of the tube 18. 'A id leak resistor 22 may be included in a circuit 23 connected in shunt relation to the grid and filament elements 16 and 17 respectively, of

the tube 18 in order to control the intensity of the negative charges which are accumulated on the grid 16. A source 24 of directsistor 26 following the variations in the characteristic of the glow discharge in the presence of sound waves, may be impressed by conductors 27 and 28 upon the input elements of a-second amplifying device (not shown), or other circuit arrangement designed to employ modulated electrical energy.

the glow discharge at times assumed an insensitive state and that, as the electrodes As hereinbefore stated, it was found that current energy may be included in the gridaged, a time was reached when the insensitherefor, the former serving as pole pieces for the latter. The 'magnet-izable yoke member 29 may belprovided with an exciting winding 31 which is energized from a source 1 32 of direct-current energy through an adjustable resistor 33. The magnetic circuit of the several magnetizable members thus contains an air gap 34" which includes the space occupied by the 'glow discharge. Hence, a magnetic field is established which is parallel to the path of theglow discharge.

An aditionaladvantage of themagnetic tions in the sensitivity of the discharge with frequency and to render the operation of the same substantially constant in the presence of air currents.

When operating my invention in the circuit of a large transmitting station); was

a low-voltage source of direct-current energy (not shown) and the primary winding 38.

of a transformer 39, -the secondary winding 41- of which is connected by conductors 42 and 43 to the input terminals 16 and 17,

respectively, of the repeater device 18, in

the manner indicated in Fig. 1. The operation of this figure is otherwise as indicated for F ig. 1.

In view of the foregoing, it is apparent that my invention embodies a translating or amplifying device which is characterized by its simplicity of design and operation. Attention is directed to the absence of moving parts,- a feature peculiar to the ordinary telephone translating device and one introducing disadvantages well known to those skilled in the art. -Other advantages of my invention will be apparent from a study of field is that it tends to decrease any variafound necessary to provide means for shield-- ing the conductors leading to the discharge electrodes, as, for instance, by including the same in cables 35 having a metallic covering. However, it was then found that the operation of the glow discharge was exceed-- ingly unsteady, since. the conductors and shields functioned as condensers, periodi-' discharge.

cally discharging across trodes and extinguishing the normal glow The operation of the glow discharge was rendered steady by' including a resistor 36 in one of the conductors, as 6, immediately adjacent to the corresponding electrode 2. The grid-conductor 14 is connected to the discharge electrode 2 through the resistor 36. v

' 9" bon dioxide and other gases Various forms of glow discharge have been established in oxygen,

with the idea of studying the effect of different gases on the operation thereof. Such experiments ashave been made seem to indicate that, for best results, nitrogen must be present in the medium immediately surrounding the discharge. w I

The arrangement shown in Fig. 3 is differ'entiated over that shown in Fig. 1 in the tariations,

provision of a different supply circuit 37 for the discharge electrodes -1 and 2 said supply circuit having such low impedance that current .variations,

are established therein when the the discharge elec-' hydrogen, car-' the foregoing description anlil the following claims.

In order to insure that the discharge will be a glow discharge and will continue to be a glow discharge, and not change into an arc, I find that the source of potential must be high and that a current limiting device must be used. In addition to the specific dimensions already stated herein, the following actual constructions are noted. In

one specific embodiment of my invention, I

employed a source of somewhat more than 4000 volts with a resistance in-series between it and the discharge device of approximately one megohm. Inanother specific embodimerit of this invention, I employed a source of 4200 volts, together with a current limiting device which restricted the current to one millimeter. The current'limiting device used in this instance was a saturation tube.

'A characteristic difference between the glow discharge and the'arc isfound in the relation of current to voltage. In the arc the current is much greaterand the voltage much smaller than in the glow discharge. Another characteristic difference is that with the glow discharge the electrodes are relatively cool, never becoming incandescent, while with an arc the electrodes are hot and .the cathode is usually more incandescent rather. than potential pressure in the vicinity of thedischargeis varied. The supply circuit .37 now includw than any portion of the arc itself.

'VVhile I have described my invention as embodied in circuit arrangements having certain specific values and while I- have shownvonly two forms of embodiment of my invention, it is apparent that various changes and modifications may be made therein without departing from the sp1r1t thereof I desire, therefore, that only such limitations shall be imposed thereon as are indicated inthe appended claims or are demanded by the prior art.

. I claim'as my invention: 1. -An amplifying device domprismg a pair of s aced copper'discharge electrodes, the space between said electrodes being open to the atmosphere, means for establishing and maintaining a glow discharge therebetween, and means for establishing a magnetic field in the space intermediate said spaced electrodes.-

2. In combination, a pair of spaced electrodes, a source of energy, conductors associating said electrodes and said energy source to provide for the formation of a glow discharge between said electrodes, means for shielding said conductors and means for preventing the resulting capacity of the condensers formed by said conductors and shielding means from-operating to render unstable said glow discharge.

3. In combination, a pair of spaced electrodes, a source of energy, conductorsassoclatlng sald electrodes and sad energy source to provide for the formation of 8.

glow discharge between said electrodes, 9 means for shielding said conductors,-and aresistor included in circuit with one of said conductors for preventing the capacity cefj fects between said conductors and said shields from operating to render unstable said glow discharge. f

4.1m a glow-discharge device,-a pair of pointed electrodes spaced apart w1th the 4 points toward each other, said points being of copper, and means for maintaining a magnetic-field in the space between said ele'ctrodes parallel to the line between said points.

-In testimony whereof, I have hereunto subscribed my name this 10th day of Novem- 35 her, 1922.

1 Pmms ITHOMASQ 7 

